Renesas ISL6524CB

Overview

ISL6524CB from Intersil is a VRM8.5-compliant quad-output power system controller integrating one voltage-mode PWM core regulator and three linear regulators in a 28-pin SOIC package. It delivers precisely regulated 1.05–1.825V (±1% DAC-programmed), 1.2V (±3%), 1.5V (±3%), and 1.8V (±3%) outputs for Intel microprocessor core, AGTL+ bus, AGP bus, and chipset core power. Designed for ATX motherboard applications with +12V, +5V, and +3.3V bias inputs.

For engineers reviewing the ISL6524CB datasheet, ISL6524CB pinout, ISL6524CB application, or ISL6524CB equivalent, key selection considerations include VRM8.5 TTL DAC compatibility, synchronous buck gate drive capability (UGATE/LGATE), triple linear regulator drive (DRIVE2/3/4), integrated overcurrent protection using MOSFET r_DS(ON), and dual Power-Good signaling (PGOOD and VTTPG) with sequenced soft-start.

Technical Context

The ISL6524CB implements a single-loop voltage-mode PWM control architecture with a 200kHz internal oscillator (±15% adjustable via RT resistor), high-bandwidth error amplifier (88dB DC gain, 15MHz GBWP), and full 0–100% duty cycle capability. Its VRM8.5-compatible 5-bit DAC (VID0–VID3, VID25) sets the core output reference with 25mV steps across 1.050V–1.825V.

Three independent linear controllers use external N-channel MOSFETs or NPN transistors, with fixed regulation points at 1.2V (VSEN2), 1.5V (VSEN3 when FIX = open), and 1.8V (VSEN4 when FIX = open), each monitored for undervoltage (75% threshold) and protected by fault latching logic. Soft-start is implemented via two dedicated current-sourced pins (SS13/SS24, 28μA each) controlling ramp timing for PWM and linear outputs independently.

Key Specifications

Pinout & Package

ISL6524CB is housed in a 28-lead SOIC package (M28.3 drawing), RoHS-compliant and Pb-free, with standard 0.050" lead pitch and 0.220" body width.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad-output VRM power controller applications.

Compared with ISL6524CB, ISL6522CB reduces output count and removes chipset core support, while RT8802AZSP shifts to multi-phase PWM architecture with no VID compatibility-neither offers pin-to-pin or functional equivalence for four-rail VRM8.5 motherboard designs.

Availability

ISL6524CB is available at Aetrix Electronics and suitable for motherboard power regulation, ATX-compliant computing platforms, and legacy Intel processor reference designs requiring stable component supply with long-term lifecycle support.

Supply support for ISL6524CB includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Intersil Corporation (now part of Renesas Electronics) is a semiconductor company specializing in precision analog, power management, and interface ICs for computing, industrial, and communications markets.

The ISL6524CB belongs to Intersil's VRM power controller product line, designed specifically for compliant, multi-rail motherboard power delivery systems supporting Intel microprocessors and AGP/PCI bus architectures.

FAQ

What is the primary function of the ISL6524CB in a motherboard power system?

The ISL6524CB serves as a quad-output power system controller that regulates four critical voltage rails: microprocessor core (via VRM8.5-compliant PWM), AGTL+ bus (1.2V), AGP bus (1.5V), and chipset core (1.8V). It integrates all control, monitoring, sequencing, and protection functions into a single 28-pin SOIC device, enabling compact, reliable, and standards-compliant motherboard power delivery. The ISL6524CB replaces multiple discrete controllers and simplifies design while meeting Intel VRM8.5 timing and accuracy requirements.

Does the ISL6524CB support VRM8.5 voltage identification (VID) protocol?

Yes, the ISL6524CB fully supports the Intel VRM8.5 VID protocol through its five TTL-compatible VID input pins (VID0–VID3 and VID25), which program the internal DAC to set the microprocessor core output voltage from 1.050V to 1.825V in precise 25mV steps. This allows direct interface with Intel Pentium III/IV processors without external level-shifting or decoding logic. The ISL6524CB's DACOUT voltage also establishes corresponding PGOOD and overvoltage protection thresholds, ensuring full VRM8.5 system compliance.

How does the ISL6524CB implement overcurrent protection without a sense resistor?

The ISL6524CB uses the upper MOSFET's intrinsic on-resistance (r_DS(ON)) as the current-sensing element. An internal 200μA current source at the OCSET pin develops a reference voltage across an external resistor (ROCSET), and the PHASE-to-UGATE voltage drop is compared against this reference. When the product of load current and r_DS(ON) exceeds the ROCSET-set threshold, the overcurrent comparator trips. This method eliminates the power loss and board space associated with a discrete current-sense resistor while maintaining accurate peak-current limiting in the ISL6524CB.

What are the roles of the SS13 and SS24 pins on the ISL6524CB?

SS13 and SS24 are dedicated soft-start timing pins with internal 28μA current sources. SS13 controls the ramp-up timing for the PWM-regulated core output (VOUT1) and the 1.5V AGP linear output (VOUT3); SS24 controls the 1.2V AGTL+ linear output (VOUT2) ramp. Each pin connects to an external capacitor to set the soft-start interval independently, enabling strict ATX sequencing-particularly the requirement that VOUT4 (1.8V chipset core) must not lag ATX 3.3V by more than 2V. This dual soft-start architecture is integral to the ISL6524CB's robust startup behavior.

Can the ISL6524CB regulate voltages other than the default 1.2V, 1.5V, and 1.8V linear outputs?

Yes-the ISL6524CB allows adjustment of the 1.5V and 1.8V linear outputs (VOUT3 and VOUT4) by grounding the FIX pin (Pin 2) and connecting external resistor dividers to VSEN3 and VSEN4. With FIX grounded, VOUT3 can be set from 1.26V up to the input voltage (e.g., +5V), and VOUT4 from ~1.7V upward. The 1.2V output (VOUT2) remains fixed unless modified externally via DRIVE2 and feedback network changes. This flexibility enables custom voltage configurations while retaining the ISL6524CB's integrated control and protection features.